Process of cementation



Patented July 7, 1936 PROCESS OF CEMENTATION Harry K. Ihrig, Milwaukee, Wis, assignor to Globe Steel Tubes 00., Milwaukee, Wis., a corporation of Delaware No Drawing. Application mm, 1934,

Serial No. 732,305

13 Claims. (01. 91-701) This invention relates to the coating and impregnating of metals, particularly iron and steel, with other metals by a process of cementation.

It has heretofore been proposed to coat a to approximately 1500 F. and held there for four hours. Nitrogen gas was introduced into the open end of the tube to displace the air. The article, after this treatment and upon cooling,

metal by processes of cementation wherein the showed a nickellzed case under the microscope metal to be coated is heated in contact with the with pure nickel on the outside and a gradual coating metal in powdered form. Under these decline of the nickel content to the inside margin prior proposals, however, extremely anhydrous of the case. On etching a section of the article conditions, high temperatures, and special proin dilute sulphuric acid, the case was plainly visions for rigid reducing atmospheres were noticeable without magnification. It was from necessary as well as long periods of heating. .005" to .025" in thickness. There was no sharp Other objections and disadvantages were also line between the case and core but a gradual inherent in these prior processes which, coupled change from the pure nickel on the outside to with the negligible degree of penetration of the iron in the core, the inward portion of the case coating metal into the grain structure of the being a nickel iron alloy. Thus a case is formed foundation metal, rendered such practices as which is firmly locked in the steel and is, in fact, well as the resultant products of little or no anintegral part of it. Crushing the impregnated practical or commercial value. article failed to show any cracking, separation, or

According to the present invention, coating and other damage or impairment to the case. impregnation are obtained at relatively low If, in the above example, copper, chromium, temperatures and with no necessity for the mainor manganese oxalate were substituted for the tenance of the extreme conditions above outnickel oxalate, the coating and impregnating lined. Furthermore, the results are superior in case would be of copper, chromium, or'manthat the depth of the coating and impregnation ganese, and should it be desired to coat and imor case is substantial and of such character as pregnate the iron or steel with an alloy of two to impart to the resultant product highly desiror more of these metals, a mixture of the organic able and advantageous characteristics such as salts of such metals would be used. superior and lasting corrosion and scale resisting I have further discovered that in carrying out properties and luster or color, rendering the inthe process, the organic salts on decomposing vention one of wide application and usefulness. generate inert and reducing gases such as carbon I have discovered that when organic salts of monoxide, carbon dioxide and hydrogen which the desired coating and impregnating metals protect the iron or steel from the air throughsuch as the formates, oxalates acetates, etc. are out the treatment, although under some condipacked about a foundation metal, such as iron tions it may be found desirable to augment this and steel for example, and the whole heated in a protection by the addition of inert or reducing closed receptacle to a temperature below the gases such as nitrogen or hydrogen from some melting point of either metal, the salts decomoutside source as in the above example. A quanpose, liberating the metal constituent of the salt tity of some suitable fluxing material such as which in turn penetrates or enters the surface ferric-chloride or copper-chloride added to or layer of the foundation metal and also forms a mixed with the organic salt appears to expedite coating layer over the surface of such metal, the penetration, although the process is entirely these layers together constituting what may aptly practical and workable without the use of an be called a case comprised of substantially pure outside inert gas to augment the natural inert metal on the outside with a gradation inward of or reducing atmosphere generated and provided alloy decreasing in richness of coating and imby the organic salts onheating. In fact, excellent pregnating metal content from the surface to results have been obtained by using merely the the interior of the foundation metal. By varycommercial organic saltsand a flux and luting ing the time and temperature of the treatment, the receptacle to prevent oxidation. Metals other the thickness or depth or the case may be varied. than iron or steel can be treated in a similar By way of example of the practice of the manner with similar results and organic salts of process, a mixture of 30 grams of nickel oxalate the desired impregnating metals other than the and one gram of iron chloride flux was packed oxalates, formates, and acetates may be used, about a low carbon steel article in a large tube the chief requirement in this regard being that closed at one end. This was inserted in a verthe selected salt be readily decomposable under tical electric furnace and the temperature raised heat to give off the desired coating and impregnating metal in atomic fineness and at the same time generate an inert or reducing gas which protect the foundation metal from the air penetration is plainly shown by photomicro-- graphs where it can be seen along and around the grain boundaries of the foundation metal, and doubtless the impregnating metal also enters the grains themselves to form a solid solution which would not show in a photomicrographbecause it would have the same grain structure as the original ferrite. Along the grain boundaries the impregnating metal appears to be in a substantially pure state, while the grains themselves are of an alloy of the foundation and impregnating metals. Such alloy, produced by my process may be termed a'cementation alloy as distinguished from an alloy produced by fusion.

I claim: 1. The process of coating and impregnating the surface layer of one metal with another metal which consists in heating the first-named metal 'under non-oxidizing conditions in contact with an organic salt of a second-named metal at a temperature below the meltingpoint of either of said metals, said organic salt being characterized by the ability to yield inert and reducing gases such as carbon dioxide, carbon monoxide and hydrogen, when decomposed as a result of said heating.

2. The process of coating and impregnating the surface layer of one metal with another metal which consists in heating the first-named metal under non oxidizing conditions in contact with an organic salt of the second-named metal such as the oxalate, formate, or acetate thereof at a temperature below the melting point of either of said metals, said organic salt being characterized by the ability to yield inert and reducing gases such as carbon dioxide, carbon monoxide and hydrogen, when decomposed as a result of said heating.

3. The process of coating and, impregnating the surface layer of iron or steel with nickel which consists in heating the iron or steel under nonoxidizing conditions in contact with an organic salt of nickel such for example as nickel-formate, nickel-oxalate, or nickel-acetate to a temperature at which the salt decomposes, said salt being characterized by the ability to yield inert and reducing gases such as carbon dioxide, carbon monoxide and hydrogen, when decomposed, liberating the nickel content thereof in the form of infinitesimally small particles which combine with the iron or steel by adhesion, intergranullar penetration, and cementation.

4. The process of coating and impregnating the surface layer of iron or steel with chromium which consists in heating the iron or steel under non-oxidizing conditions in contact with an organic salt of chromium such for example as particles which combine with the iron or steel by adhesion, intergranular penetration, and cementation.

5. The process of coating and impregnating the surface layer of iron or steel with copper is ,which consists in heating the iron or steel under 'non-oxidizing conditions in contact with an oring and impregnation in the form of'a case of 20 non-oxidizing and corrosion resisting metal, consisting of an organic salt of the latter metal decomposable under heat, said salt being characterized by the ability to yield the metal constituent thereof in atomic fineness and inert and 25 reducing gases such as carbon dioxide, carbon monoxide and hydrogen.

7. A cementation compound for the treatment of iron or steel to provide the latter with a coating and impregnation in the form of a case of 30 non-oxidizing and corrosion resisting metal, consisting of an organic salt of the latter metal decomposable under heat, said salt being characterized by the ability to yield the metal constituent thereof in atomic fineness and an inert gas'35 which protects the iron or steel from the air during the treatment.

8. A cementation mixture for the treatment of iron or steel to provide the latter with a coating and impregnation in the form of a case of 40 non-oxidizing and corrosion resisting metal, consisting of an organic salt of the latter metal decomposable under heat, and a small quantity of fluxing material, said salt being characterized by the ability to yield the metal constituent thereof 45 I inatomic fineness and an inert gas.

9. A cementation mixture for the treatment of iron or steel to provide the latter with a coating and impregnation in the form of a case comprised of an alloy of two or more non-oxidizing and cor- 50 rosion resisting metals, which mixture consists of organic salts of the latter metals decomposable under heat, said salts being characterized by the ability to yield the metal constituents thereof in atomic fineness and an inert gas.

10. A cementation mixture for the treatment of iron or steel to provide the latter with a coating and impregnation in the form of a case comprised of an alloy of two or more non-oxidizing and corrosion resisting metals, which mixture 60 consists of organic salts of the latter metals decomposable under .heat, and a. small quantity of fiuxing material, said salts being characterized by the ability to yield the metal constituent thereof in atomic fineness and inert and reducing gases such as carbon monoxide, carbon dioxide and hydrogen.

11. The process of coating and impregnating the surface layer of one metal with an alloy of two or more metals which consists in heating the first-named metal under non-oxidizing conditions incontact with organic salts-of the other metals at a temperature below the melting point of any of said metals, said salts being characterized by" the ability to decompose under heat to yield inert and reducing gases.

12. The process of coating and impregnating the surface layer of one metal with another metal which consists in heating the first-named metal under non-oxidizing conditions in contact with a heat decomposable salt of the second-named metal, said salts being characterized by the ability to yield inert and reducing gases and to liberate the metallic constituent thereof in the form of infinitesimally small particles which combine with the first-named metal to form a case of substantially pure metal on the outside and a cementation alloy of the two metals on the inside.

13. The process of coating and impregnating the surface layer of iron or steel with a metal of the group consisting of chromium, nickel, copper and manganese which consists in heating the iron or steel under non-oxidizing conditions in contact with an organic salt of an acid of the group consisting of formic acid, oxalic acid and acetic acid of the desired metal of said first named group to a temperature at which the salt decomposes, said salts being characterized by the ability to yield inert and reducing gases when decomposed, liberating the metal content thereof in the form of infinitestimally small particles which combine with the iron or steel by adhesion, intergranular penetration, ahd cementation.

HARRY K. IHRIG. 

